A new method will be evaluated for the postoperative assessment of flow in small vascular grafts. The principle of thermal clearance, using a specially designed thermistor probe, will be investigated because it will yield flow detection techniques that will be applicable regardless of graft location, structure or electrical impedance. Following initial development and calibration of the apparatus the method will be applied to the canine model. In order to allow frequent, atraumatic, non-invasive studies under physiologic conditions of rest or exercise a telemetry system will be incorporated. Flow probes and electronic hardware will be constructed in such a fashion as to permit long-term studies so that the technique can be applied to future evaluation of graft function in diverse research conditons in the experimental animal.